RE: [RFC] klibc requirements, round 2

RE: [RFC] klibc requirements, round 2

[Torrey Hoffman]

Tom Rini wrote:
> On Thu, Jan 10, 2002 at 03:18:49PM -0800, Greg KH wrote:
... 
> > 	- image viewer
> > 	- mkreiserfs
> 
> I think these are examples of misunderstanding what initramfs _can do_
> with what we (might) need a klibc to do.  
...
> These programs _might_ compile with a klibc, but I wouldn't 
> worry about
> it.  uClibc is what should be used for many of these custom 
> applications

Well, as the person who first mentioned mkreiserfs and the like,
I agree with you.  For the majority of systems out there which 
aren't using initrd now, a minimal klibc for an unmodified 
initramfs makes sense.

My concern is with the minority who are using initrd, and in
some cases a very customized initrd.  

The important thing, I think, is that it should be easy for
less-than-guru level hackers to add programs to the initramfs,
even if the program they want can't be linked with klibc.

This really comes down to: What will the build process be for
these initramfs images?

By the way, is initramfs intended to supercede initrd, or will 
they co-exist?  

Torrey

Re: [RFC] klibc requirements, round 2

[Tom Rini]

On Thu, Jan 10, 2002 at 05:50:52PM -0800, Torrey Hoffman wrote:
> Tom Rini wrote:
> > On Thu, Jan 10, 2002 at 03:18:49PM -0800, Greg KH wrote:
> ... 
> > > 	- image viewer
> > > 	- mkreiserfs
> > 
> > I think these are examples of misunderstanding what initramfs _can do_
> > with what we (might) need a klibc to do.  
> ...
> > These programs _might_ compile with a klibc, but I wouldn't 
> > worry about
> > it.  uClibc is what should be used for many of these custom 
> > applications
> 
> Well, as the person who first mentioned mkreiserfs and the like,
> I agree with you.  For the majority of systems out there which 
> aren't using initrd now, a minimal klibc for an unmodified 
> initramfs makes sense.

Okay.

> My concern is with the minority who are using initrd, and in
> some cases a very customized initrd.  

Right.  And moving that very customized initrd over to an initramfs
should be painless, once the kinks/bugs are worked out of the yet-to-be
created programs that exist in the kernel now.

> The important thing, I think, is that it should be easy for
> less-than-guru level hackers to add programs to the initramfs,
> even if the program they want can't be linked with klibc.
> 
> This really comes down to: What will the build process be for
> these initramfs images?

It's a cpio archive, occording to the draft spec hpa posted.

> By the way, is initramfs intended to supercede initrd, or will 
> they co-exist?  

I _think_ co-exist.

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Re: [RFC] klibc requirements, round 2

[H. Peter Anvin]

Followup to:  <D52B19A7284D32459CF20D579C4B0C0211CB2C@mail0.myrio.com>
By author:    "Torrey Hoffman" <torrey.hoffman@myrio.com>
In newsgroup: linux.dev.kernel
> 
> My concern is with the minority who are using initrd, and in
> some cases a very customized initrd.  
> 

They can presumably use whatever they already do, except they'll make
it into a .cpio.gz file instead of an .img.gz file.

> The important thing, I think, is that it should be easy for
> less-than-guru level hackers to add programs to the initramfs,
> even if the program they want can't be linked with klibc.
> 
> This really comes down to: What will the build process be for
> these initramfs images?
> 
> By the way, is initramfs intended to supercede initrd, or will 
> they co-exist?  

Eventually supercede; it will let us pull out an amazing amount of
crud.

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>

[RFC] klibc requirements, round 2

[Greg KH]

Hi,

Ok, now that we have a general idea that people are going to want to
stick lots of different types of programs into the initramfs, does this
change any of the initial requirement list for klibc that I sent out?

To summarize, here's a partial list of the programs people want to run:
	- mount
	- hotplug
	- busybox
	- dhcpcd
	- image viewer
	- mkreiserfs
	- partition discovery (currently in the kernel)
	- lots of other, existing in kernel code.

So on to the requirements:
  1) portable
     This is still true.
     
     dietlibc and uClibc currently do not cover the
     range of platforms that this code must run on.  For either of them
     to be used, they must be worked on.

  2) tiny
     Still true.
     
     For some people, glibc will be acceptable.  For the rest of us, we
     want something a bit smaller :) Both uClibc and dietlibc fit this
     requirement.

  3) dynamic version available
     Probably not true anymore.
     In talking with lots of people, and playing with the dynamic
     linking capabilities of different libraries, I don't think this is
     worth having as a requirement for this kind of library.

  4) not suck
     Still true :)


So, what's the available options to try to meet these requirements?

Here's some proposed solutions:
  - dietlibc / uClibc
    Nice options.  Both of these libraries are already fairly complete.
    One drawback is they are not portable to all platforms.  With some
    work, this can probably be solved.

  - klibc
    Portability can be achieved through using the kernel unistd.h file
    for the syscall logic, and having a very small _start function
    written.  For an example of this kind of code, see the initramfs
    patches from Al Viro on his ftp site:
	    ftp://ftp.math.psu.edu/pub/viro/
    This would involve writing/porting a lot of the basic library
    functions.  They could be copied from the existing libc
    implementations, but this would be a separate project, requiring
    maintenance over time, and people willing to do the work.

Is this all a good summary?  Any other comments from people?

How about responses from the dietlibc and uClibc people on the odds of
them being able to port to the remaining platforms?

In the meantime, I'll go off and play with klibc, and see if I can get
some portability based off of Al's example code.  If anyone is
interested, the code can be found at:
	http://linuxusb.bkbits.net:8088/klibc

thanks,

greg k-h

Re: [RFC] klibc requirements, round 2

[Bjorn Wesen]

On Thu, 10 Jan 2002, Greg KH wrote:
> So on to the requirements:
>   1) portable
>      This is still true.
>      
>      dietlibc and uClibc currently do not cover the
>      range of platforms that this code must run on.  For either of them
>      to be used, they must be worked on.

FWIW we (at Axis) run both uClibc and glibc for embedded Linux products,
and both work fine but obviously with different target compromises wrgds
to memory footprints, speed of porting etc. uClibc works fine with a
majority of programs relevant to us, not just a small list of useful
tools.

We have an arch/cris port of uClibc, which could be merged with the
official branch at some point.

>   3) dynamic version available
>      Probably not true anymore.
>      In talking with lots of people, and playing with the dynamic
>      linking capabilities of different libraries, I don't think this is
>      worth having as a requirement for this kind of library.

uClibc seem to work fine shared, that's how I've ran it for a while now.
When doing a "complete" linux system in 2 MB flash to put in a product,
every shared byte possible is worth to put some time on :) Granted, if the
goal is just to compile 10 small tools it might not be very useful but
since it's not that difficult to support it, and you're making yet another
libc, why not keep it flexible.

> How about responses from the dietlibc and uClibc people on the odds of
> them being able to port to the remaining platforms?

I'm sorry I must have missed why yet another libc was needed in the first
place :)

/BW

Re: [RFC] klibc requirements, round 2

[Greg KH]

On Thu, Jan 10, 2002 at 11:29:24PM +0100, Bjorn Wesen wrote:
> 
> I'm sorry I must have missed why yet another libc was needed in the first
> place :)

Please see these threads:
	http://marc.theaimsgroup.com/?t=101045445500001
	http://marc.theaimsgroup.com/?t=101051901100018
and other initramfs threads recently on this mailing list.

thanks,

greg k-h

Re: [RFC] klibc requirements, round 2

[Tom Rini]

On Thu, Jan 10, 2002 at 03:18:49PM -0800, Greg KH wrote:

> Ok, now that we have a general idea that people are going to want to
> stick lots of different types of programs into the initramfs, does this
> change any of the initial requirement list for klibc that I sent out?
> 
> To summarize, here's a partial list of the programs people want to run:
[snip]
> 	- image viewer
> 	- mkreiserfs

I think these are examples of misunderstanding what initramfs _can do_
with what we (might) need a klibc to do.  What we need a klibc for is
the lots of other, existing in kernel code, and related things which we
can't do right now, but could do (IP PNP over pcmcia wasn't possible
when I tried it ages ago, but should be when 2.5.x is over hopefully).
These programs _might_ compile with a klibc, but I wouldn't worry about
it.  uClibc is what should be used for many of these custom applications
of initramfs.  And any of the kernel code pulled out into userland
should end up being able to compile on any libc, since we'll need it in
the final root, so it would probably be in the real roots /sbin too.

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Re: [RFC] klibc requirements, round 2

[Felix von Leitner]

Thus spake Greg KH (greg@kroah.com):
>   - klibc
>     Portability can be achieved through using the kernel unistd.h file
>     for the syscall logic, and having a very small _start function
>     written.  For an example of this kind of code, see the initramfs
>     patches from Al Viro on his ftp site:
> 	    ftp://ftp.math.psu.edu/pub/viro/
>     This would involve writing/porting a lot of the basic library
>     functions.  They could be copied from the existing libc
>     implementations, but this would be a separate project, requiring
>     maintenance over time, and people willing to do the work.

Portability should be achieved by using unified syscalls, which both the
diet libc and uClibc now use.  That saves space over the unistd.h
approach.

> How about responses from the dietlibc and uClibc people on the odds of
> them being able to port to the remaining platforms?

I think I can speak for both Erik and myself when I say that we don't
hate architectures and because of that don't support them.  If we get a
chance (and maybe a little help from someone who knows those platform),
we will port our libc to that platform.

Sadly, I don't have the deep pockets to buy myself a hardware lab with a
VAX to port my libc to it.  So I (and Erik, too, obviously) would need
at least an account on one of those boxes, with gcc, binutils, strace
and gdb installed.

> In the meantime, I'll go off and play with klibc, and see if I can get
> some portability based off of Al's example code.  If anyone is
> interested, the code can be found at:
> 	http://linuxusb.bkbits.net:8088/klibc

In my eyes that is a waste of time, really.
But it's your time, so don't let that stand in your way ;)

Felix

Re: [RFC] klibc requirements, round 2

[Erik Andersen]

On Fri Jan 11, 2002 at 02:31:50PM +0100, Felix von Leitner wrote:
> > How about responses from the dietlibc and uClibc people on the odds of
> > them being able to port to the remaining platforms?
> 
> I think I can speak for both Erik and myself when I say that we don't
> hate architectures and because of that don't support them.  If we get a
> chance (and maybe a little help from someone who knows those platform),
> we will port our libc to that platform.
> 
> Sadly, I don't have the deep pockets to buy myself a hardware lab with a
> VAX to port my libc to it.  So I (and Erik, too, obviously) would need
> at least an account on one of those boxes, with gcc, binutils, strace
> and gdb installed.

Fully agreed.  Porting libc (diet or uClibc) is an issue of
hardware access, access to the instruction set docs for the arch,
access to a gnu toolchain, and (the biggest issue) an issue of
time and motivation.

> In my eyes that is a waste of time, really.
> But it's your time, so don't let that stand in your way ;)

I agree here.  dietlibc is GPL.  uClibc is LGPL.  I think they
both address the problem space pretty well.  Felix and I are
both willing to accept patches.

Lets look at it the other way...  Suppose you start making a
separate klibc.  You skip/eliminate a ton of stuff and next week
someone complains that it's missing, say, the pivot_root syscall.
So you add it.  Then the week after, someone complains that you
are missing varargs.  So you add that too.  Pretty soon, someone
will complain about how printf feature foo is missing, and they
just _need_ SuS2 wordexp compatibility, etc, etc.  Trust me when
I say you are on a very slippery slope, with a awful lot of
redundant work ahead of you.  If you want to pursue it, thats
fine, and I'll even help you a bit.  But I think that soon
enough, you will converge on what dietlibc and uClibc already
have.

 -Erik

--
Erik B. Andersen             http://codepoet-consulting.com/
--This message was written using 73% post-consumer electrons--

Re: [RFC] klibc requirements, round 2

[Alexander Viro]

On Sat, 12 Jan 2002, Erik Andersen wrote:

> On Fri Jan 11, 2002 at 02:31:50PM +0100, Felix von Leitner wrote:
> > > How about responses from the dietlibc and uClibc people on the odds of
> > > them being able to port to the remaining platforms?
> > 
> > I think I can speak for both Erik and myself when I say that we don't
> > hate architectures and because of that don't support them.  If we get a
> > chance (and maybe a little help from someone who knows those platform),
> > we will port our libc to that platform.
> > 
> > Sadly, I don't have the deep pockets to buy myself a hardware lab with a
> > VAX to port my libc to it.  So I (and Erik, too, obviously) would need
> > at least an account on one of those boxes, with gcc, binutils, strace
> > and gdb installed.

There are several VAX emulators with varying degrees of b0rkenness.
At least one of them manages to boot NetBSD...
 
> Fully agreed.  Porting libc (diet or uClibc) is an issue of
> hardware access, access to the instruction set docs for the arch,
> access to a gnu toolchain, and (the biggest issue) an issue of
> time and motivation.
> 
> > In my eyes that is a waste of time, really.
> > But it's your time, so don't let that stand in your way ;)
> 
> I agree here.  dietlibc is GPL.  uClibc is LGPL.  I think they
> both address the problem space pretty well.  Felix and I are
> both willing to accept patches.
> 
> Lets look at it the other way...  Suppose you start making a
> separate klibc.  You skip/eliminate a ton of stuff and next week
> someone complains that it's missing, say, the pivot_root syscall.
> So you add it.  Then the week after, someone complains that you
> are missing varargs.  So you add that too.  Pretty soon, someone
> will complain about how printf feature foo is missing, and they
> just _need_ SuS2 wordexp compatibility, etc, etc.  Trust me when

... at which point you tell them to bugger off.  If they refuse -
man procmailrc.  Problem solved.

Re: [RFC] klibc requirements, round 2

[Felix von Leitner]

Thus spake Alexander Viro (viro@math.psu.edu):
> > Lets look at it the other way...  Suppose you start making a
> > separate klibc.  You skip/eliminate a ton of stuff and next week
> > someone complains that it's missing, say, the pivot_root syscall.
> > So you add it.  Then the week after, someone complains that you
> > are missing varargs.  So you add that too.  Pretty soon, someone
> > will complain about how printf feature foo is missing, and they
> > just _need_ SuS2 wordexp compatibility, etc, etc.  Trust me when
> ... at which point you tell them to bugger off.  If they refuse -
> man procmailrc.  Problem solved.

I guess the point here is that you don't save anything over the diet
libc.  I went to great lengths to make sure not using printf would not
incur any overhead.  So if klibc is diet libc without printf, then using
klibc won't produce smaller binaries than using diet libc (unless you
use printf, of course, in which case klibc won't work at all).

By the way: one more architecture is now supported by the diet libc:
hp pa-risc.  Someone surprised me by sending a patch.

Felix

Re: [RFC] klibc requirements, round 2

[David Lang]

I would personally rather see dietlibc / uClibc get ported to the
remaining platforms and have them become fairly standard options for
staticly linking small programs rather then spend the effort to create a
klibc and then make it portable as well.

I would rather have the people looking at making a small, optimized libc
work on one codebase instead of scattering their efforts amoung several
:-)

while the dietlibc / uClibc may not be quite as small and optimized as a
klibc would be the fact that people are currently able to survive with
glibc indicates that the space issue probably isn't _that_ high a priority
(if klibc produces a 100K binary while dietlibc produces a 120K binary and
glibc produces a 2M binary the difference in space between klibc and
dietlibc really doesn't matter much :-)

David Lang



On Thu, 10 Jan 2002, Greg KH wrote:

> So, what's the available options to try to meet these requirements?
>
> Here's some proposed solutions:
>   - dietlibc / uClibc
>     Nice options.  Both of these libraries are already fairly complete.
>     One drawback is they are not portable to all platforms.  With some
>     work, this can probably be solved.
>
>   - klibc
>     Portability can be achieved through using the kernel unistd.h file
>     for the syscall logic, and having a very small _start function
>     written.  For an example of this kind of code, see the initramfs
>     patches from Al Viro on his ftp site:
> 	    ftp://ftp.math.psu.edu/pub/viro/
>     This would involve writing/porting a lot of the basic library
>     functions.  They could be copied from the existing libc
>     implementations, but this would be a separate project, requiring
>     maintenance over time, and people willing to do the work.
>
> Is this all a good summary?  Any other comments from people?
>
> How about responses from the dietlibc and uClibc people on the odds of
> them being able to port to the remaining platforms?
>
> In the meantime, I'll go off and play with klibc, and see if I can get
> some portability based off of Al's example code.  If anyone is
> interested, the code can be found at:
> 	http://linuxusb.bkbits.net:8088/klibc
>

Re: [RFC] klibc requirements, round 2

[Juan Quintela]

>>>>> "greg" == Greg KH <greg@kroah.com> writes:

Hi

greg> To summarize, here's a partial list of the programs people want to run:
greg> - mount
greg> - hotplug
greg> - busybox
greg> - dhcpcd
greg> - image viewer
greg> - mkreiserfs
greg> - partition discovery (currently in the kernel)
greg> - lots of other, existing in kernel code.

I still think that fsck at this point will be great.  You will
minimize the need to have the kernel special case for fsck the root fs
with respect to the rest of fs.

Later, Juan.


-- 
In theory, practice and theory are the same, but in practice they 
are different -- Larry McVoy

Re: [RFC] klibc requirements, round 2

[Alexander Viro]

On 12 Jan 2002, Juan Quintela wrote:

> >>>>> "greg" == Greg KH <greg@kroah.com> writes:
> 
> Hi
> 
> greg> To summarize, here's a partial list of the programs people want to run:
> greg> - mount

	I _really_ doubt it.  /init calling mount(2) - sure, but mount(8)?
Not really.

> greg> - hotplug
> greg> - busybox
> greg> - dhcpcd
> greg> - image viewer
> greg> - mkreiserfs
> greg> - partition discovery (currently in the kernel)

Assuming that it moves to userland, which is non-obvious.  Going other
way (i.e. clean kernel API for parsing _and_ changing partitioning)
might be better.  Current mechanisms for notifying kernel about partition
table changes are really gross.

> greg> - lots of other, existing in kernel code.

nfsroot mounting (socket/sendto/recvfrom/open/close/read/write/malloc/free/
snprintf/memcpy/strlen/mount).

> I still think that fsck at this point will be great.  You will
> minimize the need to have the kernel special case for fsck the root fs
> with respect to the rest of fs.

_Kernel_ has no special-casing of that kind.

Re: [RFC] klibc requirements, round 2

[Theodore Tso]

On Sat, Jan 12, 2002 at 09:16:21PM +0100, Juan Quintela wrote:
> >>>>> "greg" == Greg KH <greg@kroah.com> writes:
> 
> Hi
> 
> greg> To summarize, here's a partial list of the programs people want to run:
> greg> - mount
> greg> - hotplug
> greg> - busybox
> greg> - dhcpcd
> greg> - image viewer
> greg> - mkreiserfs
> greg> - partition discovery (currently in the kernel)
> greg> - lots of other, existing in kernel code.
> 
> I still think that fsck at this point will be great.  You will
> minimize the need to have the kernel special case for fsck the root fs
> with respect to the rest of fs.

The development sources for e2fsprogs will already work with diet
libc.  Unfortunately, diet libc doesn't do shared libraries, so
resulting binaries are sufficiently big that I doubt they would be
interesting for initrd and rescue floppy applications (which is why I
tried the experiment in the first place).

In any case, given that e2fsprogs is already portable to NetBSD and
Solaris (the latter so I can run purify to catch memory errors), it
shouldn't be particularly difficult to get e2fsprogs to run on some
other alternative libc.

						- Ted

Re: [RFC] klibc requirements, round 2

[Oliver Xymoron]

On Mon, 14 Jan 2002, Theodore Tso wrote:

> On Sat, Jan 12, 2002 at 09:16:21PM +0100, Juan Quintela wrote:
> > >>>>> "greg" == Greg KH <greg@kroah.com> writes:
> >
> > Hi
> >
> > greg> To summarize, here's a partial list of the programs people want to run:
> > greg> - mount
> > greg> - hotplug
> > greg> - busybox
> > greg> - dhcpcd
> > greg> - image viewer
> > greg> - mkreiserfs
> > greg> - partition discovery (currently in the kernel)
> > greg> - lots of other, existing in kernel code.
> >
> > I still think that fsck at this point will be great.  You will
> > minimize the need to have the kernel special case for fsck the root fs
> > with respect to the rest of fs.
>
> The development sources for e2fsprogs will already work with diet
> libc.  Unfortunately, diet libc doesn't do shared libraries, so
> resulting binaries are sufficiently big that I doubt they would be
> interesting for initrd and rescue floppy applications (which is why I
> tried the experiment in the first place).

Let's separate out the rescue disk and normal boot scenarios here.
Obviously the ideal for a rescue disk is to include as much useful stuff
as physically possible and that's not something we should be concerning
ourselves with for normal boot.

For normal boot (which is what we are talking about, as all booting is
moving to initramfs), we want enough code to get to the point where we
mount root read-only (no fsck!) and that means enough to load modules and
possibly get NFS up. And whatever else that's already in the kernel simply
for boot that can be moved to userspace. Nothing else.

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

Re: [RFC] klibc requirements, round 2

[Andreas Dilger]

On Jan 14, 2002  15:57 -0600, Oliver Xymoron wrote:
> On Mon, 14 Jan 2002, Theodore Tso wrote:
> > The development sources for e2fsprogs will already work with diet
> > libc.  Unfortunately, diet libc doesn't do shared libraries, so
> > resulting binaries are sufficiently big that I doubt they would be
> > interesting for initrd and rescue floppy applications (which is why I
> > tried the experiment in the first place).
> 
> For normal boot (which is what we are talking about, as all booting is
> moving to initramfs), we want enough code to get to the point where we
> mount root read-only (no fsck!) and that means enough to load modules and
> possibly get NFS up. And whatever else that's already in the kernel simply
> for boot that can be moved to userspace. Nothing else.

Actually, the whole point of Juan's suggestion was that you _don't_ want
to fsck a filesystem that is currently mounted.  There is always a
potential problem that fsck will change the on-disk data of the filesystem
in a way that is not coherent with what the kernel has in-memory, which
should force a system reboot before continuing (which most initscripts
don't do).  For ext2/ext3 this may be relatively safe (data/metadata don't
move around much), but reiserfsck cannot (or will not) fsck a mounted
filesystem at all.

It would be interesting to see if e2fsck could be linked into busybox or
another multi-call binary to avoid the overhead of the static libc linking.
I don't think there are any technical obstacles, just a matter of someone
sitting down and doing it.  It would still be pretty big (150kB or so).

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/

Re: [RFC] klibc requirements, round 2

[Oliver Xymoron]

On Mon, 14 Jan 2002, Andreas Dilger wrote:

> Actually, the whole point of Juan's suggestion was that you _don't_ want
> to fsck a filesystem that is currently mounted.  There is always a
> potential problem that fsck will change the on-disk data of the filesystem
> in a way that is not coherent with what the kernel has in-memory, which
> should force a system reboot before continuing (which most initscripts
> don't do).  For ext2/ext3 this may be relatively safe (data/metadata don't
> move around much), but reiserfsck cannot (or will not) fsck a mounted
> filesystem at all.

Interesting point. Modulo any existing LVM brokenness, we can do this with
a read-only snapshot and pivot_root afterwards. Alternately, a read-only
/bootsupport or something of the sort which contains *fsck. What we don't
want is initramfs to get big.

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

Re: [RFC] klibc requirements, round 2

[Andreas Dilger]

On Jan 14, 2002  19:26 -0600, Oliver Xymoron wrote:
> On Mon, 14 Jan 2002, Andreas Dilger wrote:
> > Actually, the whole point of Juan's suggestion was that you _don't_ want
> > to fsck a filesystem that is currently mounted.  There is always a
> > potential problem that fsck will change the on-disk data of the filesystem
> > in a way that is not coherent with what the kernel has in-memory, which
> > should force a system reboot before continuing (which most initscripts
> > don't do).  For ext2/ext3 this may be relatively safe (data/metadata don't
> > move around much), but reiserfsck cannot (or will not) fsck a mounted
> > filesystem at all.
> 
> Interesting point. Modulo any existing LVM brokenness, we can do this with
> a read-only snapshot and pivot_root afterwards. Alternately, a read-only
> /bootsupport or something of the sort which contains *fsck. What we don't
> want is initramfs to get big.

Err, you think putting the necessary LVM tools in initramfs (vgscan,
vgchange, lvcreate, liblvm) will be _smaller_ than e2fsck???  Your
"modulo" is also a very big one - I'd rather trust e2fsck than LVM
in my boot environment any day.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/

Re: [RFC] klibc requirements, round 2

[Oliver Xymoron]

On Mon, 14 Jan 2002, Andreas Dilger wrote:

> > Interesting point. Modulo any existing LVM brokenness, we can do this with
> > a read-only snapshot and pivot_root afterwards. Alternately, a read-only
> > /bootsupport or something of the sort which contains *fsck. What we don't
> > want is initramfs to get big.
>
> Err, you think putting the necessary LVM tools in initramfs (vgscan,
> vgchange, lvcreate, liblvm) will be _smaller_ than e2fsck???

No, I forgot about that dependency entirely. Doh.

> Your "modulo" is also a very big one - I'd rather trust e2fsck than LVM
> in my boot environment any day.

Fair enough. The deeper point is that the purpose of initramfs is to move
stuff out of the kernel in to userland. Ergo, this all becomes a
non-kernel issue. We do not want to be in the business here of packaging
things into the ramfs archives, we rather want to give external tools and
distros all the info they need to make intelligent choices about how to
make the kernel bootable.

Let's just try to focus on what we're taking out of the kernel in this
process and not on all the nifty stuff that can now be added to the
initial boot process.

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

Re: [RFC] klibc requirements, round 2

[Rob Landley]

On Monday 14 January 2002 11:05 pm, Oliver Xymoron wrote:

> Fair enough. The deeper point is that the purpose of initramfs is to move
> stuff out of the kernel in to userland. Ergo, this all becomes a
> non-kernel issue. We do not want to be in the business here of packaging
> things into the ramfs archives, we rather want to give external tools and
> distros all the info they need to make intelligent choices about how to
> make the kernel bootable.

The deeper issue is what portion of initramfs changes with each minor kernel 
version, and what portion stays static through a major release.

The volatile stuff (like the module tree) we will have to supply.  The static 
stuff (like the /init script, shell to run it if it's not c code, dhcp 
client, root filesystem determination, nfs mount, etc) can live in its own 
directory as long as there is a clean well-defined API that it and the kernel 
can talk to each other through.  It doesn't even have to get rebuilt, just 
scooped up into the archive.

When initramfs is required to boot, we're going to have to supply at least a 
skeleton version of it in the kernel tarball.  But if the distributions 
supply their own uncompressed initramfs tree in a well-known location 
(something like /usr/src/initramfs, perhaps) then all the kernel build has to 
do is cpio that up, add on the volatile stuff (module directory, etc), and 
hand that archive and the bzImage off to whatever the install script is that 
copies them to /boot and updates the bootloader if necessary.

If /usr/src/initramfs isn't there, then the build process should use the 
minimalist skeleton version in the kernel tarball instead.  (The skeleton's 
purpose would mostly as example code with the absolute minimum required to 
boot a fairly straightforward system, but it should work and the only way to 
really know that is to build it and try it.)  It skeleton would largely 
serve as a baseline for distributors to add to, containing the common code 
they can't really avoid having.

So when we're breaking stuff out of the kernel and putting it into initramfs, 
we move the code it into the skeleton initramfs directory, and define a clean 
API that it and the kernel can talk to each other through.  Then later, stuff 
can be dropped from the skeleton directory if we decide it doesn't need to 
live in the kernel tarball (things like klibc which have more than one 
implementation, or a micro dhcp client that not everybody really needs in 
order to boot).

So the first question is, what parts of initramfs are going to change with 
each new kernel version (I.E. the module tree), and what stuff is going to 
stay pretty stable between major releases (the /init script?)  Second 
question, what are the APIs that the stable stuff will be calling so they 
don't necessarily have to be recompiled for each new minor release?

> Let's just try to focus on what we're taking out of the kernel in this
> process and not on all the nifty stuff that can now be added to the
> initial boot process.

Let's focus on how to separate the volatile parts of initramfs that have to 
stay in the kernel tree, and the non-volatile parts that can talk to the rest 
of the kernel through cleanly defined APIs the kernel must support.

If a section of code can't talk to the kernel through a stable API, it can 
never be moved out of the kernel tree, and there's not too much point in 
moving it out of the kernel proper, really...

Rob

Re: [RFC] klibc requirements, round 2

[Alexander Viro]

On Tue, 15 Jan 2002, Rob Landley wrote:

> Let's focus on how to separate the volatile parts of initramfs that have to 
> stay in the kernel tree, and the non-volatile parts that can talk to the rest 
> of the kernel through cleanly defined APIs the kernel must support.
> 
> If a section of code can't talk to the kernel through a stable API, it can 
> never be moved out of the kernel tree, and there's not too much point in 
> moving it out of the kernel proper, really...

The whole fscking point is to _avoid_ special API.  System calls.  Normal,
usual system calls and nothing else.

And frankly, moving out of the kernel tree is the least of my worries -
if it's a normal userland code it's fine with me.

I don't see any problems with having the first component of image
generated when you build the kernel - as the matter of fact you
want that, since there is no reason to have nfsroot code there if you
don't support NFS, etc.

Re: [RFC] klibc requirements, round 2

[Oliver Xymoron]

On Tue, 15 Jan 2002, Alexander Viro wrote:

> On Tue, 15 Jan 2002, Rob Landley wrote:
>
> > Let's focus on how to separate the volatile parts of initramfs that have to
> > stay in the kernel tree, and the non-volatile parts that can talk to the rest
> > of the kernel through cleanly defined APIs the kernel must support.
> >
> > If a section of code can't talk to the kernel through a stable API, it can
> > never be moved out of the kernel tree, and there's not too much point in
> > moving it out of the kernel proper, really...
>
> The whole fscking point is to _avoid_ special API.  System calls.  Normal,
> usual system calls and nothing else.
>
> And frankly, moving out of the kernel tree is the least of my worries -
> if it's a normal userland code it's fine with me.
>
> I don't see any problems with having the first component of image
> generated when you build the kernel - as the matter of fact you
> want that, since there is no reason to have nfsroot code there if you
> don't support NFS, etc.

This is an argument for the script called by 'make install' to peek at the
config, not for the kernel to build any of the user space boot tools.

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

Re: [RFC] klibc requirements, round 2

[H. Peter Anvin]

Followup to:  <20020114125433.A1357@thunk.org>
By author:    Theodore Tso <tytso@mit.edu>
In newsgroup: linux.dev.kernel
> 
> Unfortunately, diet libc doesn't do shared libraries
> 

That would seem to be major lose, no?

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>

Re: [RFC] klibc requirements, round 2

[Erik Andersen]

On Mon Jan 14, 2002 at 12:54:33PM -0500, Theodore Tso wrote:
> 
> In any case, given that e2fsprogs is already portable to NetBSD and
> Solaris (the latter so I can run purify to catch memory errors), it
> shouldn't be particularly difficult to get e2fsprogs to run on some
> other alternative libc.

It works just fine with uClibc..  Both shared and static,

 -Erik

--
Erik B. Andersen             http://codepoet-consulting.com/
--This message was written using 73% post-consumer electrons--

Re: [RFC] klibc requirements, round 2

[Alexander Viro]

On Thu, 10 Jan 2002, Greg KH wrote:

>   - klibc
>     Portability can be achieved through using the kernel unistd.h file
>     for the syscall logic, and having a very small _start function
>     written.  For an example of this kind of code, see the initramfs
>     patches from Al Viro on his ftp site:
> 	    ftp://ftp.math.psu.edu/pub/viro/
>     This would involve writing/porting a lot of the basic library
>     functions.  They could be copied from the existing libc
>     implementations, but this would be a separate project, requiring
>     maintenance over time, and people willing to do the work.

Note: said patches are against relatively old 2.4 trees.  They demonstrate
that quite a few things can be moved to userland, however it's mostly
proof-of-concept stuff.  In particular
	* in the final variant we let the loader to leave archive(s)
in core, rather than linking them into the kernel image.
	* nfsroot.c is *crap*
	* quite a few things are currently done better (modulo moving
init/do_mounts.c code in userland process).  IOW, reduction to syscalls
could be (and already is) done better than in these patches.

I'll put current version of that stuff for public testing, but that
will happen after the current mess with kdev_t/struct block_device *
will be resolved...